In proteins such as keratin, a cystine bond forming an intraprotein or interprotein link is characterized as R—C—S—S—C—R in which the C—R represents the cystine amino acid as part of a protein polypeptide and the two chains are joined by the S—S bond. This S—S bond can be broken by reduction of the Sulfur to S—H or it can be broken by oxidation to give a sulfonic acid residue, SOx. Other possibilities include a substitution in which another sulfur containing moiety such as mercaptoethanol or thioglycolate are bonding to one or both sides of the cystine bond. Of these, all but the oxidation reaction are reversible and the cystine disulfide can be reformed. Oxidation of the sulfur blocks reformation of the cystine S—S bond. Lanthionization has been known for use in cosmetic treatments (see U.S. Pat. Nos. 3,908,672 and 3,971,391). A lanthionized disulfide loses one of the sulfur atoms and would be represented as R—C—S—C—R. This is also an irreversible reaction allowing one to control the amount of subsequent oxidation of the material.
In the case of keratin proteins, it is often desirable to manipulate the character of the cysteine sulfurs by partially oxidizing the material and then neutralizing the product to produce a hydrogel forming material. By controlling the number of oxidized sulfurs, the characteristics of the hydrogel material can also be controlled.
Lanthionization as disclosed for use in cosmetic treatments was done in an aqueous medium using hydroxide base, specifically LiOH, frequently at elevated temperatures and was applied to living human hair. The present inventors have found that application of this living hair technology to keratin containing raw materials and particularly wool fabric produced materials that were too fragile for certain applications or in some cases completely degraded. The present disclosure expands the use of lanthionization processes to a means of preparing new and improved materials for biomedical and other applications.